Pleurisy, inflammation affecting the pleura, the serous membrane covering the lungs and chest walls. The disease may be excited by exposure to cold, or arise from injury, or be associated with tubercular or malignant disease, or arise in the course of certain fevers or in association with kidney or heart mischief. The chief symptoms are pain in the side, aggravated on taking a deep breath, fever, cough, and difficulty of breathing. Two varieties of pleurisy are described: dry pleurisy and pleurisy with effusion. In the former case the inflammation is accompanied by the formation of lymph, constituting what is called false membrane, and the rubbing of the diseased pleural surfaces against one another produces the characteristic "friction sound" which is heard in this condition on auscultation of the chest. In pleurisy with effusion, serous fluid is effused and accumulates in the pleural cavity, the underlying lung becomes compressed and collapsed, and on physical examination of the chest certain characteristic signs are discoverable. There is usually dulness on percussion up to the level at which the fluid stands, the breathing sounds are faint, and sometimes what is known as cvgophony is heard by the auscultator when the patient speaks. When the effused fluid becomes purulent, the condition of empyema is said to exist.